1. Filed of the Invention
The present invention related to a simple, portable anchor device for providing an anchor point to resist the reaction forces associated with conveying a load between two substantially horizontal surfaces with different elevations. More specifically, the invention relates to a portable anchor device which provides an anchor point above and behind the proximal edge of the upper surface.
2. Description of the Prior Art
The conveyance of loads between lower and upper horizontal surfaces includes lifting loads on and off vehicles or moving them up and down stairs. Such transport can often be facilitated by a means with mechanical advantage such as a winch with a flexible line. However, application of such means requires an immovable anchor point to resist the reaction forces associated with the action of the motive force on the load. Furthermore, it is preferable that the anchor point be located above and behind the proximal edge of the upper horizontal surface.
This requirement is exemplified in U.S. Pat. No. 5,183,372 dated Feb. 2, 1993, granted to Dinverno for "Van-Mounted Service Carts for Skilled Tradesmen", in which a winch means is anchored within a motor vehicle and is used to winch a service cart across a ramp means between the ground and the vehicle bed. While such anchor points can be created in a specific location by means such as clamping, welding or bolting, there are many locations where such affixation is impractical or impossible. Moreover, such anchor points are not portable and may require strength assessment of the structural base for the anchor point in each application.
Another common requirement of the approach suggested by the aforesaid patent is that the ramp means must be secured to resist the forces produced by load traversal across the ramp. Again, solutions such as clamping or bolting preclude simple and broad application.
A useful aspect for reducing the motive force requirement for load conveyance is maintenance of collinearity between the motive force and load advance throughout the transport process. In U.S. Pat. No. 5,203,668 dated Apr. 20, 1993, granted to Marmur for an "Apparatus for Loading and Unloading of a Container Structure or Other Loads with Respect to a Truck Body or Trailer", this aspect is partially achieved by a pivotable upper frame which can apply motive force in a combined upward and forward direction somewhat collinear with load advance. However, the collinearity is imperfect and the upper frame is not portable.
Finally, if a flexible line used to apply motive force to a load on a ramp or incline is not taut when the load begins descent, unrestrained load advance may cause damage or injury.
Accordingly, it is an object of the present invention to provide an anchor point to resist the reaction forces associated with conveyance of a load between horizontal surfaces with different elevations, in a device which is portable and does not require affixation to the surfaces or structures between which the load is conveyed. Furthermore, in a preferred embodiment, a ramp means and more specifically, a ramp means secured to resist the forces of load traversal is not required.
Another object of the present invention is that the anchor point be located above and behind the proximal edge of the upper horizontal surface. The invention may also permit application of motive force which is substantially collinear with load advance until the load is supported on a horizontal surface. A further object of the invention is that it will prevent load descent until a flexible line controlling load advance is taut.